Single action din rail latch

ABSTRACT

An electronics module includes a latch with a first latch portion and a second latch portion. The latch portions move between a latched position and an unlatched position. A spring is located between the first and second latch portions and biases the first and second latch portions in first and second directions. The first latch portion comprises an actuation portion located externally from the housing and that is adapted to be manually engaged and moved linearly in the second direction to move the first latch portion from its latched position toward its unlatched position. The second latch portion includes a resilient tail with a locator tab that seats in either a first receiving location or a second receiving location of the first latch portion and that is selectively deflectable to disengage the locator tab from the second receiving location so that the spring moves the latch to the latched configuration.

FIELD

The present development relates to an improved latch for an electronicsmodule, and to an electronics module including the improved latch. Inone application, the electronics module is an input/output (i/o) moduleor a controller module or the like provided as part of an industrialautomation control system, but other types of electronics modules arecontemplated and are within the scope of the present development. In oneapplication, the latch is particularly adapted to selectively andreleasably mate with a 35 mm×7.5 mm top hat DIN rail, i.e., a railprovided in accordance with EN 50022, BS 5584, DIN 46277-3 (referred toherein as a “DIN rail”), but the latch can be alternatively configuredto mate with any other rail or structure including first and secondedges or flanges to be engaged be the latch.

BACKGROUND INFORMATION

The subject matter disclosed herein relates to Industrial automation andother types of electronics modules often include a latch or latch systemfor selectively and releasably connecting the electronics module to anassociated mounting structure such as a DIN rail. While known latches ofthis type are generally suitable and effective, a need has beenidentified for a new and improved latch assembly or latching system thatis more convenient and effective than known latch assemblies.

SUMMARY

In accordance with one aspect of the present development, an electronicsmodule includes a housing with a rear face comprising a recess adaptedto receive an associated mounting rail. The recess comprises first andsecond opposite edges. A latch assembly is connected to the housing andis adapted for selectively releasably securing the housing an associatedmounting rail located in the recess. The latch assembly comprises: afirst latch portion movably connected to the housing and comprising alocking tab adapted to capture a first associated DIN rail flange insaid recess; a second latch portion movably connected to the housingadjacent the first latch portion and comprising a second locking tabadapted to capture a second associated DIN rail flange in the recess.The first and second latch portions are movable relative to each otherto and between: (i) a latched configuration where the first and secondlatch portions are located in respective latched positions in which thefirst and second locking tabs project respectively beyond the first andsecond opposite edges of the recess and partially obstruct the recess;and (ii) an unlatched configuration where the first and second latchportions are located in respective unlatched positions in which thefirst and second locking tabs are spaced farther apart from each otheras compared to the latched configuration. The latch assembly furtherincludes first and second springs, wherein the first spring exerts abiasing force on said first latch portion that urges both the first andsecond latch portions in a first direction relative to the housing whenthe first and second latch portions are located in the unlatchedconfiguration, and wherein the second spring exerts a biasing force thaturges said first latch portion in said first direction and urges saidsecond latch portion in a second direction that is opposite said firstdirection.

In accordance with another aspect of the present development, anelectronics module comprises a housing including a rear face comprisinga recess comprising first and second opposite edges and an inner region.A latch assembly is connected to the housing and is adapted forselectively releasably securing the housing an associated mounting raillocated in the recess. The latch assembly comprises: a first latchportion movably connected to the housing and comprising a locking tabadapted to capture a first flange of the associated mounting rail insaid recess; and a second latch portion movably connected to the housingand slidably abutted with the first latch portion. The second latchportion comprises a second locking tab adapted to capture a secondflange of the associated mounting rail in the recess. The first andsecond latch portions movable relative to each other to and between: (i)a latched configuration of the latch assembly in which the first andsecond latch portions are located in respective latched positions andthe first and second locking tabs are spaced apart from each other by afirst distance Y1 and project respectively beyond the first and secondopposite edges of said recess and partially obstruct the recess; and(ii) an unlatched configuration of the latch assembly in which the firstand second latch portions are located in respective unlatched positionsand the first and second locking tabs are spaced apart from each otherby a second distance Y2, wherein Y2>Y1. The electronics module includesfirst and second springs. The first spring is operatively locatedbetween the housing and the latch assembly and biases the first latchportion in a first direction when the latch assembly is arranged in theunlatched configuration. The second spring is operatively locatedbetween the first and second latch portions and biases the first latchportion in the first direction and biases the second latch portion in asecond direction opposite the first direction. The first latch portionincludes an actuation portion that projects and is located externallyfrom the housing and that is adapted to be manually engaged and movedlinearly to move the first latch portion from its latched positiontoward its unlatched position.

In accordance with a further aspect of the present development, anelectronics module includes a housing with a rear face comprising arecess with first and second opposite edges and an inner region. A latchassembly is connected to the housing and is adapted for selectivelyreleasably securing the housing to an associated mounting rail locatedin the recess. The latch assembly comprises: a first latch portioncomprising a locking tab adapted to capture a first flange of theassociated mounting rail in the recess; and a second latch portionslidably abutted with the first latch portion, the second latch portioncomprising a second locking tab adapted to capture a second flange ofthe associated mounting rail in the recess. The first and second latchportions are movable relative to each other between: (i) a latchedconfiguration of the latch assembly in which the first and second latchportions are located in respective latched positions and the first andsecond locking tabs are spaced apart from each other by a first distanceY1 and project respectively beyond said first and second opposite edgesof said recess and partially obstruct said recess; and (ii) an unlatchedconfiguration of the latch assembly in which the first and second latchportions are located in respective unlatched positions and the first andsecond locking tabs are spaced apart from each other by a seconddistance Y2, wherein Y2>Y1. A spring is operatively located between thefirst and second latch portions and biases the first latch portion in afirst direction and biases the second latch portion in a seconddirection opposite the first direction. The first latch portioncomprises an actuation portion located externally from the housing andthat is adapted to be manually engaged and moved linearly in the seconddirection to move the first latch portion from its latched positiontoward its unlatched position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an electronics module including a latch systemin accordance with an embodiment of the present development;

FIG. 2 is a rear isometric view of the electronics module of FIG. 1,showing the module operatively connected to an associated DIN rail;

FIG. 3 is a simplified side section view of the module and DIN rail ofFIG. 2, showing the latch system in its latched or locked configuration;

FIG. 4 is similar to FIG. 3, but shows the latch system in its unlatchedor unlocked configuration;

FIGS. 5A, 5B, and 5C are side section views of a latch assembly portionof the latch system of the module shown in FIGS. 1-4, with FIG. 5Ashowing the latch assembly in its latched configuration, FIG. 5C showingthe latch assembly in its unlatched configuration, and FIG. 5B showingthe latch assembly in an intermediate configuration between the latchedand unlatched configurations;

FIG. 6 provides an exploded side view of the first (primary) and second(secondary) latch portions or latch members of the latch assembly ofFIGS. 5A-5C;

FIG. 7 is a greatly enlarged partial isometric view of an outer portionof the first/primary latch portion;

FIG. 8 is an enlarged isometric view of the first and second latchportions operatively connected together in their latched configuration;

FIG. 9 is an enlarged isometric view of the first and second latchportions operatively connected together and located in their in theirunlatched configuration.

DETAILED DESCRIPTION

FIG. 1 is a side view of an electronics module M including a latchsystem L in accordance with an embodiment of the present development.FIG. 2 is a rear isometric view of the electronics module M, showing themodule operatively connected to an associated DIN rail D. Theillustrated electronics module M is an input/output module of anindustrial automation system, but the module can be any other type ofelectronics modules such as an adapter module, controller module, oranother type of module of an industrial automation system, or anelectronics module not related to an industrial automation system.

FIG. 3 is a simplified side section view of the module M and DIN rail D,showing the latch system L in its latched or locked configuration, andFIG. 4 is similar to FIG. 3, but shows the latch system L in itsunlatched or unlocked configuration. Referring to all of FIGS. 1-4, theelectronics module M comprises a one-piece or multi-piece moldedpolymeric or metallic (e.g. formed, cast and/or extruded aluminum orother metal) housing 10 that defines an interior space 12 that receivesand retains one or more electronic components such as one or moreprinted circuit boards PCB comprising a microprocessor P such as an ASICor general purpose microprocessor and/or other electronic circuitryadapted and programmed to perform a desired electronic function. It isoften desirable to secure the module M to an associated supportstructure such as a DIN rail or other support structure in an operativeposition as shown in FIGS. 2 and 3 and to selectively disengage andseparate the module M from the DIN rail or other support structure, andthe latch system L is provided for such purposes. To simplify thedescription, the associated support structure will be described hereinas the illustrated DIN rail D, which comprises first and secondlongitudinally extending edges or flanges DF1,DF2 (FIG. 2), but othersupport structures are contemplated and are within the scope of thepresent development.

With continuing reference to FIGS. 1-4, the housing 10 of the module Mcomprises or defines a recess R in a rear face MR thereof, and therecess R is dimensioned to closely receive the DIN rail D therein asshown, with the first and second DIN rail flanges DF1,DF2 locatedrespectively adjacent first (lower) and second (upper) opposite edgesR1,R2 of the recess R, with minimal clearance space between the DIN railedges DF1,DF2 and the recess edges R1,R2. The recess R is open on itsopposite lateral left and right sides so that the DIN rail D extendsthrough the recess, and the recess includes in inner wall R3.

The latch system L of the module M comprises a latch assembly LAcomprising first and second latch members or latch portions LP1,LP2 thatselectively engage the first and second DIN rail flanges DF1,DF2,respectively, for capturing and retaining the DIN rail flanges in therecess R for operative connection of the module M to the DIN rail D.

Referring now particularly to FIGS. 3 and 4, the first and second latchportions LP1,LP2 can be seen, along with other components of the latchassembly LA including a first spring S1 that is operatively engaged orassociated with the first latch portion LP1 and a second spring S2 thatis operatively engaged or associated with/between both the first andsecond latch portions LP1,LP2. The second spring S2 exerts biasingforces on the latch assembly LA that urges the first and second latchportions LP1,LP2 in opposite first and second directions X1,X2 towardtheir respective latched positions and, thus, urges the latch assemblyLA toward its latched configuration (FIG. 3). The first spring S1 exertsa biasing force on the first latch portion LP1, at least when the firstlatch portion LP1 is located in its unlatched position and the latchassembly is in its unlatched state, that urges the latch assembly LA(both the first and second latch portions LP1,LP2) in the firstdirection X1 when and the latch assembly LA is arranged in its unlatchedconfiguration to maintain the latch assembly LA in its required positionrelative to the housing 10. The first and second latch portions LP1,LP2are selectively manually movable relative to each other against thebiasing forces of the second spring S2 to place the latch assembly LA inits unlatched configuration (FIG. 4). When the latch assembly LA islocated in its latched position, the first and second latch portionsLP1,LP2 thereof are each located in respective latched positions, andwhen the latch assembly is located in its unlatched position, the firstand second latch portions LP1,LP2 thereof are each located in respectiveunlatched positions.

With reference now also to FIGS. 5A-5C and 6, the first latch portionLP1 preferably comprises a one-piece molded polymeric structure thatcomprises an elongated linear main portion LP1 a and an inner end LP1 blocated adjacent the first edge R1 of the recess R. The inner end LP1 bof the first latch portion LP1 comprises a first locking tab T1 adaptedto engage and retain the first DIN rail flange DF1 in the recess R. Themain portion LP1 a of the first latch portion LP1 extends adjacent theinner wall R3 of the recess R from its inner end LP1 b to an outer endLP1 c that is located external to the housing 10. The outer end LP1 cincludes or defines an actuator portion or actuator tab AT adapted to beengaged by a user's thumb or finger or otherwise manually engaged by auser to move the latch assembly LA from its latched to its unlatchedconfiguration as described below. In the illustrated embodiment, themain portion LP1 a of the first latch portion LP1 is exposed and atleast partially defines the recess inner wall R3.

The second latch portion LP2 also preferably comprises a one-piecemolded polymeric construction that comprises a main portion LP2 a and aninner end LP2 b located adjacent the second edge R2 of the recess R. Theinner end LP2 b of the second latch portion LP2 comprises a secondlocking tab T2 adapted to engage and retain the second DIN rail flangeDF2 in the recess R. The main portion LP2 a of the second latch portionLP2 lies adjacent and preferably slidably abuts the main portion LP1 aof the first latch portion LP1. The second latch portion LP2 furthercomprises a flexible, resilient tail portion LP2 t connected to the mainportion LP2 a and that extends to an outer end LP2 c located external tothe housing 10 and adjacent the outer end LP1 c and actuator portion/tabAT of the first lock portion LP1. The resilient tail portion LP2 tnormally lies adjacent and abuts the first lock portion LP1, but theresilient tail portion LP2 t is selectively deflectable away from thefirst lock portion LP1 in a deflection direction XD (see FIG. 5B) asrequired for the latch assembly LA to move between its latched andunlatched configurations.

The first and second locking tabs T1,T2 are located in respectiveextended positions and project into the recess R beyond the first andsecond recess edges R1,R2, respectively, when the latch assembly LA islocated in its latched configuration as shown in FIG. 3 so that thefirst and second DIN rail flanges DF1,DF2 are respectively capturedbehind the first and second locking tabs T1,T2, i.e., between the firstand second locking tabs T1,T2 and the inner wall R3 of the recess R.When the latch assembly LA is located in its unlatched configuration asshown in FIG. 4, the first and second locking tabs T1,T2 are located inrespective retracted positions where they are retracted relative to thefirst and second recess edges R1,R2, respectively, so that the first andsecond locking tabs are flush with or recessed relative to the first andsecond recess edges R1,R2 so that the first and second DIN rail flangesDF1,DF2 are able to move freely out of (or into) the recess R withoutbeing obstructed by the locking tabs T1,T2. The first and second lockingtabs T1,T2 are thus spaced apart from each other by a first distance Y1when the latch assembly LA is located in its latched configuration(FIGS. 3 & 5A), and are spaced apart from each other by a seconddistance Y2 that is greater than the first distance Y1 (i.e., Y2>Y1)when the latch assembly LA is located in its unlatched configuration(FIGS. 4 & 5C).

The first spring S1 is operatively located between the inner end LP1 bof the first lock portion LP1 and the housing 10. In the illustratedembodiment, the spring is maintained in a free or unloaded state whenthe latch assembly LA is arranged in its latched configuration or state,but it can also be partially compressed/loaded in this position of thelatch assembly. In the illustrated example, the first spring S1 becomesloaded/compressed and biases the first latch portion LP1 (and also thesecond latch portion LP2 as described below) in the first direction X1when the latch assembly LA is arranged in its unlatched configuration orstate to ensure that the first and second latch portions LP1,LP2 areproperly positioned relative to the housing 10 when the latch assemblyLA is configured in its unlatched state. The second spring S2 isoperatively located between the first and second latch portions LP1,LP2and biases the second latch portion LP2 in a second direction X2relative to the first latch portion toward its latched position suchthat the second locking tab T2 is biased toward its extended (latched)position, and the second spring S2 also biases the first latch portionLP1 in the first direction X1 relative to the second latch portion LP2.

As shown in FIGS. 5A-5C, 6, and 7, the second latch portion LP2comprises a locator tab LT that projects from the tail portion LP2 t,and the main portion LP1 a of the first latch portion LP1 comprisesfirst and second spaced-apart apertures, recesses or other receivinglocations RL1,RL2 (see also FIG. 7) that are adapted to receive andretain the locator tab LT. When the latch assembly LA is arranged in itslatched configuration, the locator tab LT is located in the firstreceiving location RL1, and when the latch assembly LA is arranged inits unlatched configuration, the locator tab LT is located in the secondreceiving location RL1. The receiving location RL1,RL2 in which thelocator tab LT is seated controls the distance (Y1,Y2) between the firstand second locking tabs T1,T2. The locator tab LT is shaped to include atapered outer surface LT1 oriented toward the outer end of the firstlatch portion LP1. Accordingly, relative sliding movement between thefirst and second latch portions LP1,LP2 that occurs when the latchassembly LA is in its latched state and the first latch portion LP1moves in the second direction X2 while the second latch portion isconstrained from moving in the second direction X2 due to contact withthe housing 10 will cause the locator tab tapered surface LT1 to bearagainst the first latch portion LP1 and deflect the resilient tailportion LP2 t away from the first latch portion LP1 in the deflectiondirection XD as shown in FIG. 5B such that the locator tab LT iswithdrawn from and exits the first receiving location RL1. The locatortab LT will automatically seat in the second receiving location RL2 andthe resilient tail portion LP2 t will resiliently return to undeflectedstate when the second receiving location RL2 is registered with/movesinto registration with the locator tab LT as shown in FIG. 5C.

When the locator tab LT is seated in the second receiving locations RL2as shown in FIG. 5C, the locator tab LT prevents the second spring S2from moving the second latch portion LP2 in the second directionrelative to the first latch portion LP1, but ensures that the secondlatch portion LP2 will move together with the first latch portion LP1 inthe first direction X1 under the force of the first biasing spring S1.However, engagement between the second latch portion LP2 and the housing10 prevents both of the first and second latch portions LP1,LP2 frommoving in the first direction X1 under the biasing force of the firstspring S1 beyond a desired distance, so that the latch assembly LA isrestrained or maintained in its unlatched configuration and positiononce the locator tab LT seats in the second receiving location and thefirst and second latch portions LP1,LP2 move in the first direction X1until the second latch portion LP2 abuts the housing 10. In particular,when the locator tab LT is seated in the second receiving location RL2(latch assembly LA unlatched), the first and second latch portionsLP1,LP2 are allowed to move as a unit in the first direction X1 underthe force f the first spring S1 until the second bite tooth T2 is movedto its retracted position relative to the second edge R2 of the recessR, but the first and second latch portions LP1,LP2 are prevented frommoving in the first direction X1 beyond such retracted location of thesecond bite tooth T2 to ensure that the first bite tooth T1 is alsolocated in its retracted position relative to the first edge R1 of therecess R.

When the locator tab LT is seated in the first receiving location RL1(latch assembly LA latched), the locator tab LT prevents movement of thefirst and second latch portions LP1,LP2 relative to each other inrespective first and second directions X1,X2 as would decrease thedistance Y1, and the latch portions LP1,LP2 are properly located intheir latched positions relative to the housing 10 by engagement of thefirst and/or second latch portions LP1,LP2 with the housing 10.

FIGS. 8 and 9 respectively show the first and second latch portionsLP1,LP2 in their latched and unlatched positions, and it can be seenthat the second latch portion LP2 comprises at least one wing W (twowings W are shown in the illustrated embodiment) adapted to abut themodule housing 10 to limit or constrain movement of the second latchportion LP2 in the second direction X2 under force of the second springS2, and to limit movement of both the first and second latch portionsLP1,LP2 in the first direction X1 when they are located in their latchedand unlatched positions. Likewise, the first latch portion LP1 includesone or more structures such as wings W2 that constrain movement of thefirst latch portion LP1 in the first and second directions X1,X2.

The first and second locking tabs T1,T2 each comprise a tapered outersurface T1 a,T2 a (FIG. 6) that diverges as it extends away from therecess inner wall R3 such that upon abutment of a DIN rail flangeDF1,DF2 therewith, the first latch portion LP1 will be moved linearly inthe second direction X2 relative to the housing 10 and relative to thesecond latch portion LP2 against the biasing force of the second springS2, and the second latch portion LP2 will be moved linearly in the firstdirection X1 relative to the housing 10 and relative to the first latchportion LP1 against the biasing force of the second spring S2 so thatthe DIN rail D is received in the module recess R even when the latchassembly LA is arranged in its latched configuration, i.e., the module Mcan be mounted on the DIN rail even when the latched assembly ispositioned in its latched configuration. It should be noted thatmovement of the second latch portion LP2 in the first direction X1relative to the first latch portion LP1 is allowed due to the taperedsurface LT1 of the locator tab LT and due to the fact that the resilienttail portion LP2 t is able to deflect in the deflection direction XD sothat the locator tab LT moves at least partially or completely out ofthe first receiving location RL1. Once the DIN rail flanges move intothe recess past the locking tabs T1,T2, the latch portions LP1,LP2 willreturn to their latched positions under force of the second spring S2 tocapture the DIN rail in the recess R. Also, the locking tabs T1,T2 aredimensioned such that the movement of the first and second latchportions LP1,LP2 relative to each other in the respective second andfirst directions is not of sufficient magnitude to cause the secondreceiving location RL2 to move into registration with the locator tab LTas would cause the first and second latch portions LP1,LP2 to becomeengaged with each other in the unlatched configuration.

In use, the latch assembly LA is moved from its latched configuration(FIGS. 3 & 5A) to its unlatched configuration (FIGS. 4 & 5C) upon auser's manual movement of the first latch portion LP1 linearly in thesecond direction X2 by depressing the actuator tab AT (FIG. 5B). Whenthe first latch portion is fully depressed, the locator tab LT will movefrom the first receiving location RL1 (FIG. 5A) into the secondreceiving location, and the latch assembly LA will settle and remainlocked in its unlatched configuration when the user's manual pressure isreleased from the actuator tab AT, and the first spring S1 will moveboth the first and second latch portions LP1,LP2 as a unit relative tothe housing 10 in the first direction X1 to their proper unlatchedlocation. This unlatched state can be useful if a module M includesmultiple latch assemblies LA that need to be maintained in an unlatchedstate to separate the module M from a DIN rail D. When the user desiresto reset the latch assembly LA from its unlatched condition (FIG. 5C) toits latched configuration (FIG. 5A), the user manually deflects or movesthe resilient tail portion LP2 t of the second latch portion LP2 in thedeflection direction XD until the locator tab LT exits the secondreceiving location RL1, at which time the second spring S2 will move thesecond latch portion LP2 in the second direction X2 relative to thefirst latch portion LP1 and/or the second spring S2 will move the firstlatch portion LP1 in the first direction X1 relative to the second latchportion LP2 until the locator tab LT again seats in the first receivinglocation RL1 so that the first and second latch portions LP1,LP2 arelocated in their respective latched positions as shown in FIG. 5A.

The present development thus provides and electronics module including alatch system that allows for one-handed operation/single-pointactuation, does not require a screwdriver or other tool to operate,utilizes linear movement for latching rather than pivoting or rotationalmovement, provides positive tactile feedback when moving between itslatched and unlatched configurations, is able to be locked in an open orunlatched configuration, and that is more convenient and effective thatknown latch assemblies.

In the preceding specification, various embodiments have been describedwith reference to the accompanying drawings. It will, however, beevident that various modifications and changes may be made thereto, andadditional embodiments may be implemented, without departing from thebroader scope of the invention as set forth in the claims that follow.The specification and drawings are accordingly to be regarded in anillustrative rather than restrictive sense.

The following is claimed:
 1. An electronics module comprising: a housingincluding a rear face comprising a recess adapted to receive anassociated mounting rail, said recess comprising first and secondopposite edges; a latch assembly connected to said housing and adaptedfor selectively releasably securing said housing an associated mountingrail located in said recess, said latch assembly comprising: a firstlatch portion movably connected to said housing and comprising a lockingtab adapted to capture a first associated DIN rail flange in saidrecess; a second latch portion movably connected to said housingadjacent said first latch portion and comprising a second locking tabadapted to capture a second associated DIN rail flange in said recess;said first and second latch portions movable relative to each other toand between: (i) a latched configuration where said first and secondlatch portions are located in respective latched positions in which saidfirst and second locking tabs project respectively beyond said first andsecond opposite edges of said recess and partially obstruct said recess;and (ii) an unlatched configuration where said first and second latchportions are located in respective unlatched positions in which saidfirst and second locking tabs are spaced farther apart from each otheras compared to the latched configuration; first and second springs,wherein said first spring exerts a biasing force on said first latchportion that urges both said first and second latch portions in a firstdirection relative to said housing when said first and second latchportions are located in said unlatched configuration, and wherein saidsecond spring exerts a biasing force that urges said first latch portionin said first direction and urges said second latch portion in a seconddirection that is opposite said first direction.
 2. The electronicsmodule as set forth in claim 1, wherein said second spring isoperatively engaged between said first and second latch portions.
 3. Theelectronics module as set forth in claim 2, wherein: said first latchportion comprises an actuation portion located external to said housingand adapted to be manually engaged to move said first latch portion insaid second direction from its latched position toward its unlatchedposition; and, said second latch portion comprises a resilient tailportion that lies adjacent said first latch portion and that comprises alocator tab that engages a first receiving location of said first latchportion when said first and second latch portions are located in theirrespective latched positions, and that engages a second receivinglocation of said first latch portion when said first and second latchportions are located in their respective unlatched positions.
 4. Theelectronics module as set forth in claim 3, wherein: said first latchportion is selectively manually movable in said second direction fromits latched position toward its unlatched position such that said firstlatch portion slides relative to said second latch portion, saidresilient tail is deflected in a deflection direction in response tocontact between said locator tab and said first latch portion, and saidlocator tab moves from said first receiving location to said secondreceiving location when said locator tab moves into registration withsaid second receiving location; engagement of said locator tab with saidsecond receiving location couples said second latch portion to saidfirst latch portion for movement in said first direction under force ofsaid first spring such that said second latch portion moves with saidfirst latch portion in said first direction to its unlatched positionwhen said first spring moves said first latch portion in said firstdirection; and engagement of said second latch portion with said housinglimits movement of said first and second latch portions in said firstdirection when said locator tab is located in said second receivinglocation.
 5. The electronics module as set forth in claim 4, whereinsaid resilient tail is selectively manually deflectable to withdraw saidlocator tab from said second receiving location when said first andsecond latch portions are located in said latched configuration, whereinsaid second spring moves said first latch portion in said firstdirection to said latched position of said first latch portion when saidlocator tab is withdrawn from said second receiving location.
 6. Theelectronics module as set forth in claim 5, wherein said first andsecond latch portions are movable relative to each other against saidsecond biasing force of said second spring in said second and firstdirections toward their unlatched positions, respectively, to allow theassociated mounting rail to move into said recess when said first andsecond latch portions are arranged in their latched configuration. 7.The electronics module as set forth in claim 6, wherein said locator tabcomprises a tapered outer surface oriented toward the actuation portionof the first latch portion and that extends away from said actuationportion as it extends away from said second latch portion, wherein saidtapered outer surface contacts said first latch portion upon movement ofsaid first latch portion relative to said second latch portion in saidsecond direction such that said resilient tail portion is deflected insaid deflection direction and said locator tab is at least partiallywithdrawn from said first receiving location.
 8. An electronics modulecomprising: a housing including a rear face comprising a recess, saidrecess comprising first and second opposite edges and an inner region; alatch assembly connected to said housing and adapted for selectivelyreleasably securing said housing an associated mounting rail located insaid recess, said latch assembly comprising: a first latch portionmovably connected to said housing and comprising a locking tab adaptedto capture a first flange of the associated mounting rail in saidrecess; a second latch portion movably connected to said housing andslidably abutted with said first latch portion, said second latchportion comprising a second locking tab adapted to capture a secondflange of the associated mounting rail in said recess; said first andsecond latch portions movable relative to each other to and between: (i)a latched configuration of said latch assembly in which said first andsecond latch portions are located in respective latched positions andsaid first and second locking tabs are spaced apart from each other by afirst distance Y1 and project respectively beyond said first and secondopposite edges of said recess and partially obstruct said recess; and(ii) an unlatched configuration of said latch assembly in which saidfirst and second latch portions are located in respective unlatchedpositions and said first and second locking tabs are spaced apart fromeach other by a second distance Y2, wherein Y2>Y1; first and secondsprings, wherein said first spring is operatively located between saidhousing and said latch assembly and biases said first latch portion in afirst direction when said latch assembly is arranged in said unlatchedconfiguration, and wherein said second spring is operatively locatedbetween said first and second latch portions and biases said first latchportion in said first direction and biases said second latch portion ina second direction opposite the first direction; said first latchportion comprising an actuation portion that projects externally fromsaid housing and that is adapted to be manually engaged and movedlinearly to move said first latch portion from its latched positiontoward its unlatched position.
 9. The electronics module as set forth inclaim 8, wherein said second latch portion comprising a resilient tailportion that lies adjacent said first latch portion and that comprises alocator tab that engages a first receiving location of said first latchportion when said first and second latch portions are located in theirrespective latched positions, and that engages a second receivinglocation of said first latch portion when said first and second latchportions are located in their respective unlatched positions.
 10. Theelectronics module as set forth in claim 9, wherein said second latchportion is constrained from moving together with said first latchportion in said second direction when said actuation portion movedlinearly in said second direction to move said first latch portion fromits latched position toward its unlatched position, and wherein saidresilient tail portion of said second latch portion deflects away fromsaid first latch portion in a deflection direction to allow said locatortab to exit said first receiving location to allow linear movement ofsaid first latch portion relative to said second latch portion when saidactuation portion moved linearly in said second direction to move saidfirst latch portion from its latched position toward its unlatchedposition
 11. The electronics module as set forth in claim 10, wherein:said locator tab of said second latch portion moves from said firstreceiving location to said second receiving location when said actuationportion is engaged to move said first latch portion in said seconddirection relative to said second latch portion, and; engagement of saidlocator tab with said second receiving location couples said secondlatch portion to said first latch portion for movement with said firstlatch portion in said first direction when said actuator portion isreleased and said first spring moves said first latch portion in saidfirst direction to its unlatched position.
 12. The electronics module asset forth in claim 11, wherein engagement of said second latch portionwith said housing limits movement of said first and second latchportions in said first direction under force of said first spring whensaid locator tab is located in said second receiving location such thatsaid latch assembly is located in said unlatched configuration.
 13. Theelectronics module as set forth in claim 12, wherein said resilient tailcomprises an outer end located external to said housing, said resilienttail selectively manually movable in said deflection direction when saidlatch assembly is arranged in said unlatched configuration to move saidlocator tab out of said second receiving location such that said secondspring moves said first latch portion in said first direction relativeto said second latch portion to the latched position of said first latchportion.
 14. The electronics module as set forth in claim 13, whereinsaid locator tab comprises a tapered outer surface oriented toward theactuation portion of the first latch portion and that extends away fromsaid actuation portion as it extends away from said second latchportion, wherein said tapered outer surface is engaged by said firstlatch portion upon movement of said first latch portion relative to saidsecond latch portion in said second direction such that said resilienttail portion is deflected in said deflection direction.
 15. Theelectronics module as set forth in claim 14, wherein said first andsecond locking tabs comprise respective tapered surfaces that divergeaway from each other as they extend away from said inner region of saidrecess such that said first and second latch portions are moved in saidsecond and first directions, respectively, when said first and secondlocking tabs are contacted by the first and second flanges of theassociated mounting rail upon insertion of the associated mounting railinto the recess when said latch assembly is arranged in its latchedconfiguration.
 16. An electronics module comprising: a housing includinga rear face comprising a recess, said recess comprising first and secondopposite edges and an inner region; a latch assembly connected to saidhousing and adapted for selectively releasably securing said housing anassociated mounting rail located in said recess, said latch assemblycomprising: a first latch portion comprising a locking tab adapted tocapture a first flange of the associated mounting rail in said recess; asecond latch portion slidably abutted with said first latch portion,said second latch portion comprising a second locking tab adapted tocapture a second flange of the associated mounting rail in said recess;said first and second latch portions movable relative to each otherbetween: (i) a latched configuration of said latch assembly in whichsaid first and second latch portions are located in respective latchedpositions and said first and second locking tabs are spaced apart fromeach other by a first distance Y1 and project respectively beyond saidfirst and second opposite edges of said recess and partially obstructsaid recess; and (ii) an unlatched configuration of said latch assemblyin which said first and second latch portions are located in respectiveunlatched positions and said first and second locking tabs are spacedapart from each other by a second distance Y2, wherein Y2>Y1; a springoperatively located between said first and second latch portions thatbiases said first latch portion in a first direction and that biasessaid second latch portion in a second direction opposite the firstdirection; said first latch portion comprising an actuation portionlocated externally from said housing and that is adapted to be manuallyengaged and moved linearly in said second direction to move said firstlatch portion from its latched position toward its unlatched position.17. The electronics module as set forth in claim 16, wherein said secondlatch portion comprising a resilient tail portion that lies adjacentsaid first latch portion and that comprises a locator tab that engages afirst receiving location of said first latch portion when said first andsecond latch portions are located in their respective latched positions,and that engages a second receiving location of said first latch portionwhen said first and second latch portions are located in theirrespective unlatched positions.
 18. The electronics module as set forthin claim 17, wherein said resilient tail portion deflects away from saidfirst latch portion in a deflection direction and said locator tab exitssaid first receiving location when said latch assembly is arranged insaid latched configuration and said first latch portion is movedrelative to said second latch portion in said second direction inresponse to contact between said first latch portion and said locatortab that urges said resilient tail portion in said deflection direction.